Communication devices such as wireless communication devices, that simply may be named wireless devices, may also be known as e.g. User Equipments (UEs), mobile terminals, wireless terminals and/or Mobile Stations (MS). A wireless device is enabled to communicate wirelessly in a wireless communication network that typically is a cellular communications network, which may also be referred to as a wireless communication system, or radio communication system, sometimes also referred to as a cellular radio system, cellular network or cellular communication system. The communication may be performed e.g. between two wireless devices, between a wireless device and a regular telephone and/or between a wireless device and a server via a Radio Access Network (RAN) and possibly one or more Core Networks (CN), comprised within the wireless communication network. The wireless device may further be referred to as a mobile telephone, cellular telephone, laptop, Personal Digital Assistant (PDA), tablet computer, just to mention some further examples. Wireless devices may be so called Machine to Machine (M2M) devices or Machine Type of Communication (MTC) devices, i.e. a device that is not necessarily associated with a conventional user, such as a human, directly using the device.
The wireless device may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and/or data, via the RAN, with another entity, such as another wireless device or a server.
The cellular communication network covers a geographical area which is divided into cell areas, wherein each cell area is served by at least one base station, or Base Station (BS), e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is typically identified by one or more cell identities. The base station at a base station site provides radio coverage for one or more cells. A cell is thus associated with a geographical area where radio coverage for that cell is provided by the base station at the base station site. Cells may overlap so that several cells cover the same geographical area. By the base station providing or serving a cell is meant that the base station provides radio coverage such that one or more wireless devices located in the geographical area where the radio coverage is provided may be served by the base station in said cell. When a wireless device is said to be served in or by a cell this implies that the wireless device is served by the base station providing radio coverage for the cell. One base station may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the wireless device within range of the base stations.
In some RANs, several base stations may be connected, e.g. by landlines or microwave, to a radio network controller, e.g. a Radio Network Controller (RNC) in Universal Mobile Telecommunication System (UMTS), and/or to each other. The radio network controller, also sometimes termed a Base Station Controller (BSC) e.g. in GSM, may supervise and coordinate various activities of the plural base stations connected thereto. GSM is an abbreviation for Global System for Mobile Communication (originally: Groupe Special Mobile).
UMTS is a third generation mobile communication system, which may be referred to as 3rd generation or 3G, and which evolved from the GSM, and provides improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for wireless devices.
General Packet Radio Service (GPRS) is a packet oriented mobile data service on the 2G and 3G cellular communication system's global system for mobile communications (GSM).
Enhanced Data rates for GSM Evolution (EDGE) also known as Enhanced GPRS (EGPRS), or IMT Single Carrier (IMT-SC), or Enhanced Data rates for Global Evolution is a digital mobile phone technology that allows improved data transmission rates as a backward-compatible extension of GSM.
High Speed Packet Access (HSPA) is an amalgamation of two mobile telephony protocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), defined by the 3rd Generation Partnership Project (3GPP), that extends and improves the performance of existing 3rd generation mobile telecommunication networks utilizing the WCDMA. Such networks may be named WCDMA/HSPA.
In 3GPP Long Term Evolution (LTE), which may be referred to as 4th generation or 4G, base stations, which may be referred to as eNodeBs or eNBs, may be directly connected to other base stations and may be directly connected to one or more core networks.
The 3GPP has undertaken to evolve further the UTRAN and GSM based radio access network technologies, for example into evolved UTRAN (E-UTRAN) used in LTE.
The expression downlink, which may be abbreviated DL, is used for the transmission path from the base station to the wireless device. The expression uplink, which may be abbreviated UL, is used for the transmission path in the opposite direction i.e. from the wireless device to the base station.
Machine Type of Communication (MTC) has in recent years, especially in the context of the Internet of Things (IoT), shown to be a growing market segment for cellular technologies, especially for GSM/EDGE with its more or less global coverage, ubiquitous connectivity and price competitive devices. Realization of IoT benefit from utilizing cellular technologies and GSM technology is of great, perhaps of greatest, interest to utilize at least initially. In general it is desirable to be able to (re)use existing wireless communication systems and cellular technologies for new type of devices such as MTC devices. An MTC device is typically a wireless device that is a self and/or automatically controlled unattended machine and that is typically not associated with an active human user in order to generate data traffic. A MTC device is typically much more simple, and associated with a more specific application or purpose, than and in contrast to a conventional mobile phone or smart phone. MTC involve communication to and/or from MTC devices, which communication typically is of quite different nature and with other requirements than communication associated with e.g. conventional mobile phones and smart phones. In the context of and growth of the IoT it is evidently so that MTC traffic will be increasing and thus needs to be increasingly supported in wireless communication systems.
Problems related to (re)using existing technologies and systems is e.g. that the requirements for the new type of devices typically is different than conventional requirements, e.g. regarding the type and amount of traffic, performance etc. Existing systems have not been developed with these new requirements in mind. Also, traffic generated by new type of devices will typically be in addition to conventional traffic already supported by an existing system, which existing traffic typically needs to continue to be supported by and in the system, preferably without any substantial disturbance and/or deterioration of already supported services and performance.
Any modifications need of existing systems and technology should of course be cost efficient, such as enabled by low complexity modifications, and preferably allowing legacy devices already being employed to continue to be used and co-exist with the new type of devices in one and the same wireless communication network.
Extended Coverage GSM (EC-GSM) is e.g. discussed in GP-151039, “New Work Item on Extended Coverage GSM (EC-GSM) for support of Cellular Internet of Things (CIoT_EC_GSM)”, Ericsson L M, Intel, Gemalto N. V., MediaTek Inc., TeliaSonera AB, Sierra Wireless, S.A., Telit Communications S.p.A., ORANGE, Nokia Networks, Alcatel Lucent. Cellular Internet of Things (IoT), is e.g. discussed in 3GPP TR 45.820 V13.0.0, “Cellular System Support for Ultra Low Complexity and Low Throughput Internet of Things”.
EC-GSM e.g. has the intention to improve coverage with 20 dB, to improve battery life time, keeping a minimum bitrate and to decrease device complexity. On the control channels the coverage is improved by for example using blind repetitions of radio blocks while on the data channels the coverage is improved using a combination of blind repetitions and Hybrid Automatic Repeat Request (HARQ) retransmissions of radio blocks.
One objective with EC-GSM is to be energy efficient to improve the battery life time in the devices, i.e. called mobile stations in GSM. One way of doing this is to reduce the amount of signaling between the mobile station and the network, especially reducing transmission from the mobile station since transmission in extended coverage using blind physical layer repetitions is very energy consuming.
When the mobile station accesses the network due to paging or due to data transmission, the mobile starts by transmitting an access request on the random access channel. The access request includes an estimate of the downlink coverage class as experienced by the mobile station at that time and also the access request allows the network to estimate a Timing Advance (TA) value to be used by the mobile station for uplink transmissions on an assigned Temporary Block Flow (TBF).
When the mobile station has released a TBF and entered a so called Ready State it monitors the access grant channel for a downlink assignment, from a BSS, in case of any downlink data arrival in the network and which data is targeted for the mobile station. During the Ready State the mobile station is known to the core network, in particular to the SGSN, on a cell level and can be reached by an access grant message directly instead of first being paged and then by transmitting an access request message to the network.
If data arrives in the network to be transmitted in the downlink, the mobile station will receive a downlink assignment message from the network, or in particular the BSS. Due to mobility and that tens of seconds may have passed since the latest uplink transmission occurred, the TA value assigned to the mobile station might be obsolete. The network has then the opportunity to request for a packet control acknowledgment message, sent as access bursts, giving the network an opportunity to estimate a new TA value.